This invention relates to a metallic product having a dark, nonreflective and nonflaking surface, and to a method of manufacturing the surface.
The metallic product(s) of this invention, that is, having a dark, nonreflective and nonflaking surface have nondecorative utility, for example as a surgical needle. A surgical needle having a dark and nonreflective surface is more visible at and around a wound site having a restrictive field of view, than a needle having a shiny and reflective stainless steel surface. That the dark and nonreflective surface of the needle must also be nonflaking is important, if not critical, so as not to introduce any foreign, extraneous, and possibly toxic substance into the wound.
The metallic product(s) having a dark, nonreflective and nonflaking surface may also be useful in diagnostic and analytical testing, for example where the absorption of an amount of light can be measured as a function of the increase in the temperature of the metallic product.
It is to be understood that the term "dark" in this specification is synonomous with the term "black", and further that the terms "dark", "black", "nonreflective" (or nonreflecting), and "nonflaking" in this specification have the same meaning as used in the prior art. Please see, e.g., a disclosure of black nickel plating in "Metals Handbook 8th Edition" vol. 2 pages 432 and 435, T. Lyman, Ed., Amer. Soc. For Metals, OH, U.S.A. 1964, which is incorporated herein by reference.
One embodiment of this invention is an improved metallic product manufactured from a non-300 series stainless steel. The improvement comprises the surface of the metallic product being dark and nonflaking.
Other embodiments of this invention are an improved metallic product having a dark surface and manufactured from a non-300 series stainless steel. One of the improvements comprises the dark surface of the metallic product being nonflaking. Another improvement comprises the dark surface of the metallic product being nonreflective and nonflaking.
In all of the above described improvements, the dark, nonreflective and nonflaking surface of the metallic product is nondecorative.
Specific embodiments to all of the improvements described above are wherein: the stainless steel is selected from or substantially equal to a member of the group consisting of martensitic and ferritic steels; the stainless steel is selected from or substantially equal to the 400 series; the stainless steel is selected from or substantially equal to types 420, 420F, 440 or 455; and the atomic composition of the metallic product surface does not essentially contain zinc.
A method of manufacturing a metallic product from a non-300 stainless steel, the surface of the metallic product being dark and nonflaking, has been invented. The method comprises:
(a) selecting the type of stainless steel and forming it into a product having the desired configuration; PA0 (b) submersing the product into a liquid comprising a strong acid; PA0 (c) substantially maintaining a constant temperature of the liquid while the product is submersed; PA0 (d) maintaining the product in the constant temperature liquid for a sufficient period of time to make the surface dark; and PA0 (e) removing the product from the constant temperature liquid. PA0 (a) selecting a stainless steel from, or substantially equal to a member of the group consisting of martensitic and ferritic steels, and forming the stainless steel selected into a product having the desired configuration; PA0 (b) submersing the product into a solution comprising a strong acid and water, the anion of the acid being monovalent; PA0 (c) substantially maintaining a constant temperature of the solution while the product is submersed; PA0 (d) maintaining the product in the constant temperature solution for a sufficient period of time to make the surface dark and nonreflective; and PA0 (e) removing the product from the constant temperature solution. PA0 (a) selecting a stainless steel from, or substantially equal to a member of the group consisting of the 400 series, and forming the stainless steel selected into a product having the desired configuration; PA0 (b) submersing the needle into a solution of nitric acid and water; PA0 (c) substantially maintaining a constant temperature of about 180.degree..+-.10.degree. F. of the solution while the product is submersed; PA0 (d) maintaining the product in the constant temperature solution for up to about 40 minutes; PA0 (e) removing the product from the constant temperature solution; and PA0 (f) neutralizing any residual and nonreacted acid remaining on the dark, nonreflective and nonflaking surface of the product.
In one embodiment, the method comprises the additional step of (f) neutralizing any residual and nonreacted acid remaining on the dark and nonflaking surface of the metallic product. In a specific embodiment, the neutralizing step comprises rinsing the dark and nonflaking surface of the metallic product with water; and drying the product.
In another embodiment, step (a) includes after forming the metallic product: removing any residual nonmetallic impurities remaining on the surface of the product. In still another embodiment, the temperature of the liquid in the substantially maintaining step is above ambient temperature.
Also, a method of manufacturing a metallic product from a stainless steel, the surface of the product being dark, nonreflective and nonflaking has been invented. The method comprises:
In one embodiment, the method comprises the additional step of (f) neutralizing any residual and nonreacted acid remaining on the dark, nonreflective and nonflaking surface of the metal product. In a specific embodiment, the neutralizing step comprises rinsing the dark, nonreflective and nonflaking surface of the metal product with water; and drying the product.
In another embodiment, step (a) includes after forming the metallic product: removing any residual impurities selected from the group consisting of greases, oils and mixtures thereof remaining on the surface of the product. In still another embodiment, the temperature of the solution in the substantially maintaining step is at about 180.degree. F..+-.10.degree. F.
Another method of manufacturing a metallic product from a stainless steel, the surface of the product being dark, nonreflective and nonflaking has been invented. The method comprises:
In one embodiment, the solution in the submersing step comprises about 50 percent by weight of nitric acid.
In another embodiment, the neutralizing step comprises: submersing the metallic product in a dilute base; first removing the product from the base; and second removing any residual and nonreacted base remaining on the dark, nonreflective and nonflaking surface of the product. In a specific embodiment, the base is ammonium hydroxide.
In a further embodiment, the second removing substep of step (f) comprises rinsing the dark, nonreflective and nonflaking surface of the metallic product with a drying agent; and drying said product. In a specific embodiment, the drying agent is ethanol.
In yet a further embodiment, step (a) includes after forming the metallic product: removing any residual impurities selected from the group consisting of greases, oils and mixtures thereof remaining on the surface of the product.